Device for perfoming hydrodynamic action on wellbore walls

ABSTRACT

The proposed invention relates to wellbore technologies and is intended to produce action on productive rock. Device for hydrodynamic action on wall of a well comprising a casing jointed with the pipe conduit directly or via a roller support and inside of which the mechanism for cavitating of flow of a liquid, mechanism for directing and splitting of the flow and mechanism for interrupting of the discharge jets are sequentially placed. The mechanism for cavitating of flow of a liquid is made in form of an auto-oscillating system. And specifically it can be made in a form of a ball with its diameter ratio to inner diameter of the casing of 0.9-0.98 and a limiter of axial motion; or a ball with its diameter ratio to inner diameter of the casing less than 0.9 and a limiter of axial motion in form of a coil spring lower end of which is rigidly connected to the casing and the upper end of which has a seat for the ball; or a cone the nose of which is directed counter flow, which cone is placed into a diffuser providing a clearance to let the liquid flowing and a freedom for the cone to move axially; or a butterfly valve freely rotating around transversely shaft and the halves of which are oppositely convex in respect of the rotation axis of said valve. The mechanism for interrupting of the discharge jets is made in form of the cylindrical roller bodies placed in the casing equidistantly or non-equidistantly by a separator wheel and resting on a ball working as both a roller support and a float valve. And the number of said cylindrical bodies is either (n+1) or (n−1) where (n) is a number of outlet orifices.

FIELD OF USE

[0001] The proposed invention relates to wellbore technologies and isintended to produce action on the reservoir rock to intensify inflowrate of reservoir fluids into wellbore or the intake capacity of thereservoir rock, as appropriate, to decolmatate (liberate fine materialsfrom) porous rock, to clean filters or tubes from dirt and variousdeposits, to create cavities in a wellbore wall via eroding of the rockby jets of liquid.

PRIOR ART

[0002] A device is known of a “roto-jet” type [U.S. Pat. No 4,919,204,1990] which is suspended on a roller support at the lower end of atubing or coil tubing string. It comprises a casing where the flow of aliquid pressurized by a pump splits into three or more jets ejectinginto a well through semi tangential holes equipped with the nozzleinserts. Due to hydrodynamic head of the jets the wellbore wall orcasing or lift tubing can be cleaned from dirt or deposits. The devicerotates due to jets reaction.

[0003] One can refer to the following general shortcomings of thisdevice:

[0004] 1) The pressure head of the jet often is insufficient foreffective cleaning of the tubes or wellbore wall;

[0005] 2) The possibility is not provided to produce cavitation erosionwhich is the most effective method of the tube or wellbore wallcleaning.

[0006] A device is also known [U.S. Pat. No 5,505,262, 1996] to producepulsating flow of liquid which device comprises a casing connected witha tubing or coil tubing string and inside of which a mechanism is placedto direct and split the flow. Said mechanism is made as a rolling ballwhich sequentially closes outlet orifices.

[0007] This device by principle of its action appears to be the mostrelevant technical solution to the proposed one and therefore isselected as a prototype. The main shortcomings of the prototype are thefollowing:

[0008] 1) The device, at its outlet, transforms the stationary flow intoa pulsating flow that increases the hydraulic jetting effect of the jetsaction, but is some cases it still is insufficient to destroy corrosionproducts or extract the solid particles that close the fluid passes ordestroy the rock at a wellbore wall;

[0009] 2) The possibility is not provided to employ cavitational effectin interaction of jets with surface of tubes or wellbore wall;

[0010] 3) The mechanism of interrupting the flow, which is made in aform of a ball element driven into motion by a vortex flow created abovethe ball, will not be capable to shift the ball closing the outletorifice when it is stuck by differential pressure. It makes the devicegenerally non-serviceable.

DESCRIPTION OF THE INVENTION

[0011] Goal of the proposed invention is providing of highereffectiveness of hydrodynamic action on the wellbore wall due tocavitation of the flow of liquid at elevated hydrostatic pressure bypartially or fully breaking of the liquid flow continuity, and reductionof losses of hydraulic power of pumps to implement this process.

[0012] This goal is achieved due to that in the device, comprising acasing connected with or without a rotational support to a tubing insideof which a mechanism is placed to cause cavitation of the flow ofliquid, a mechanism is provided for directing and splitting of the flowand a mechanism is provided for interrupting of the discharge jets. Thesaid mechanisms are sequentially placed from the top of the device down,and the said mechanism for cavitating of the liquid flow is made in formof an auto-oscillating system.

[0013] In particular, the mechanism causing cavitation of the liquidflow can be made in a form of a ball with its diameter ratio to innerdiameter of the casing of 0.9-0.98 and comprising a limiter of axialmotion, or in form of a ball with its diameter ratio to inner diameterof the casing less than 0.9 and comprising a limiter of axial motion inform of a coil spring lower end of which is rigidly connected to thecasing and the upper end of which has a seat for the ball. Thecavitation mechanism can be made in form of a cone the nose of which isdirected counter flow, which cone is placed into a diffuser providing aclearance to let the liquid flowing and having a freedom to moveaxially, or in form of a butterfly valve freely rotating aroundtransversely axis and the halves of which are oppositely convex inrespect of the rotation axis of said valve. Mechanism for interruptingof the discharge jets is made in form of the cylindrical roller bodiesplaced in the casing equidistantly or non-equidistantly by a separatorwheel and resting on a ball working as both a roller support and a floatvalve. And the number of said cylindrical bodies is either (n+1) or(n−1) where (n) is a number of outlet orifices.

BRIEF DESCRIPTION OF DRAWINGS

[0014] The drawings illustrate various examples of embodiments of theproposed device and the device assemblies.

[0015] In the FIGS. 1, 2, 3, and 4 the embodiments of the device areshown representing different designs of the cavitation mechanismoperating in auto-oscillating mode.

[0016] In the FIG. 5 a device is shown where mechanism for interruptingof the discharge jets is represented.

[0017] In the FIG. 6 an assembly of the device is shown comprising oneof possible cavitation mechanisms, mechanism for directing and splittingof the flow and the proposed mechanism for interrupting of the dischargejets.

[0018]FIG. 1 shows the embodiment of the device comprising a casing 1inside of which a cavitation mechanism is placed, which cavitationmechanism is made in form of a ball 2 placed on a roller or slidingsupport 3 which support is a limiter of axial motion of the ball.

[0019]FIG. 2 shows the embodiment of the device comprising a casing 1inside of which a cavitation mechanism is placed, which cavitationmechanism is made in form of a ball 2 placed on a support which supportis a limiter of axial motion of the ball and which is made in form of aspring 4. The lower end of the spring 4 is rigidly fixed in the casing 1and the upper end has a seat 5 for the ball 2.

[0020]FIG. 3 shows the embodiment of the device comprising a casing 1part of which is made in form of a diffuser 6 where a cone 7 is placedto form a cavitation mechanism. The cone 7 allows a clearance with awall and has a stem 8 which can move in the stopper 9. The stopper 9 hasholes 10. In spacing between the cone 7 and the stopper 9 a cavitationcavity 11 is formed.

[0021]FIG. 4 shows the embodiment of the device comprising a casing 1inside of which a cavitation mechanism is placed, which cavitationmechanism is made in form of a butterfly valve 13 freely rotating aroundtransversely shaft 12. The valve consists of two halves which areoppositely convex in respect of the rotation shaft 12. The ends of theshaft are fixed in the casing 1.

[0022]FIG. 5 shows the placement down flow of the cavitation mechanismof a mechanism for interrupting of the discharge jet. On a stationarysleeve 14 that is an extension of the casing 1, a casing 15 is placedconcentrically. In the annulus between the casing 15 and sleeve 14 thecylindrical roller bodies 16 are placed separated by a separator wheel17.

[0023] The cylindrical roller bodies 16 work as both the radial rollerbearing and jets interrupter. Said cylindrical roller bodies 16 rest ona ball 18 which works as both the roller support and a float valveclosing the outlet opening 19. In the casing 15 the tangential dischargejet holes 20 are made.

[0024]FIG. 6 shows an assembly of the device comprising mechanism forcavitating of flow of a liquid, mechanism for directing and splitting ofthe flow and mechanism for interrupting of the discharge jets. Thedevice consists of the casing 1 inside of which a cavitation mechanismis placed, which cavitation mechanism is made in form of a ball 2 placedon a support 3 as in the embodiment shown in the FIG. 1. End of thecasing 1 is made in a form of a sleeve 14 on which a casing 15 is set.The sleeve_14, casing 15 and the cylindrical roller bodies 16 form theshown in the FIG. 5 mechanism for splitting and directing of the flowand also interrupting of the discharge jets.

[0025] Variants of the Embodiments of the Invention

[0026] Device comprising mechanism for cavitating of the flow of liquidin form of a ball and a limiter of axial motion of the ball (FIG. 1) andknown as rotocavitator works as follows.

[0027] Flow of liquid pumped into a well through a pipe (or string ofpipes) flows around the ball 2 which ball is placed in a casing 1jointed with the said pipe. Below the ball (down flow) a cavitationalcavity is formed. Due to acceleration of the flow in clearance betweenthe ball and wall of the casing 1 the pressure there decreases inaccordance with the Bernoulli's law and the ball 2 moves in radialdirection until it reaches the wall of the casing 1. In this moment aclearance becomes open at opposite side of the ball 2 and part of thecavitational cavity is cut and entrained by the flow. It causessplitting of that part of the cavitational cavity into smaller bubbleswhich bubbles are then carried by the fluid through the tangential sideoutlet orifices and implode when reach an obstacle (wall of the pipe orborehole). Due to reactive forces of jets the device, being connected tothe pipe (string of pipes) via a roller support 3, rotates and thus thecircular treatment of the pipe wall or borehole is provided. Axialtravel of the device in the well is provided via standard running downor pulling out of the string of tubes.

[0028] Device comprising mechanism for cavitating of the flow of liquidin form of a ball placed on a spring support (FIG. 2) works as follows.

[0029] The ball 2 with its diameter ratio to inner diameter of thecasing less than 0.9 is flowed around by a flow of liquid and involvedby it into circular motion (rolling along the inner wall of the casing)due to varying clearance between the ball and casing 1. Centrifugalforce due to weight of the ball 2, conditions of flowing the ball 2around by the down going flow and friction at the wall cause the ballmoving up counter flow. However because of non-stationary nature of theflow the ball stalls then and is entrained by the flow downward. Spring4 accepts and dampens the hit by the ball 2. When the ball hits theobstacle and stops, the cavitational cavity separates from it and isentrained by the flow. After that the process is repeated.

[0030] Device comprising mechanism for cavitating of the flow of liquidin form of a cone (FIG. 3) works as follows.

[0031] Flow of liquid pumped into a well through a pipe (or string ofpipes) flows around a cone 7 placed into a diffuser 6 with a clearance.Below the cone a decompression zone and then the cavitation cavity 11 isformed. The cone 7 with a stem 8 having opportunity to move in thestopper 9 self-oscillates in axial direction. It provides separation ofparts of the cavitation cavity 11 and entraining of them in form ofbubbles through holes 10 in the stopper 9 and then through thetangential side outlet orifices into a well where they implode whenreaching an obstacle.

[0032] Device comprising mechanism for cavitating of the flow of liquidin form of a butterfly valve (FIG. 4) works as follows.

[0033] When liquid flows the butterfly valve 13 allowed to rotate on atransverse shaft 12 rigidly fixed in the casing 1 turns with its flatparallel to the direction of the flow. But the oppositely directedconvex sides of the valve constrict the flow channel resulting in atorque causing periodic closing of the flow path by the butterfly valve.It results in breaking of the continuity of the flow and formation of acavity which is entrained by the flow downward once the valve 13 turnsby 90° and then goes through the tangential side outlet orifices into awell where they implode when reaching an obstacle.

[0034] Device comprising mechanism for interrupting of the discharge jetin form of cylindrical roller bodies (FIG. 5) works as follows.

[0035] The tangential discharge jets produce reactive rotation of thecasing 15 which casing is concentrically placed on a sleeve 14 rigidlyconnected to the end of the casing 1. This sleeve joins the mechanismfor interrupting of the discharge jet with the mechanism for cavitatingof flow of liquid. The cylindrical roller bodies 16 are placed in theannulus between the rotating casing 15 and stationary sleeve 14 and areseparated by a separator wheel 17 rigidly connected to the sleeve 14.These cylindrical roller bodies work as both the radial roller bearingand jets interrupter. Said cylindrical roller bodies 16 rest on a ball18 which works as both the roller support and a float valve. The floatvalve is required to provide filling of the pipe (string of pipes) withthe liquid when it runs into a well because otherwise the liquid canpenetrate into it only through tangential discharge jet holes 20. Butwithout the float valve it can happen that said discharge jet holes areplugged and the pipes in the string would be collapsed by hydrostaticpressure.

[0036] The known kinds of hydrodynamic action on the wall of a boreholeare based on a hydraulic giant effect or effects of shock action of apulsing jet on an obstacle including the cumulative effect. Theseinteractions are realized in a homogeneous media (liquid) and requireconsuming of high hydraulic power to provide maximum possible speed ofthe discharge jet.

[0037] Combining the mechanism for cavitating of flow of liquid intodevice for hydrodynamic action on the wall of a borehole allows toobtain a two phase media—a gas-liquid system where gas bubbles existduring very short time because they implode due to hydrostatic pressure.And high speed of discharge jets allow them to leave the device casingand reach the obstacle (wall of a borehole or pipe) where the bubblesimplode and produce required work. When the bubble implodes a localnegative pressure is created upto 1000 MPa followed with a micro shockwave propagating into ambient liquid. It enables higher effectiveness ofthe cavitation jet to clean or eroding of the surface it interacts with.The imploding bubbles allow easily extract colmatants from porous orfractured rock: water drops, clay or sand particles. And circulation ofliquid in the well transports them to the surface. The back micro shockwave produces micro cracks in the rock and thus opens new paths andimproves permeability of the productive rock in bottom hole zone.

[0038] Problem in cavitating of a flow of liquid in wells, wherehydrostatic pressure can be of 20-40 MPa, is how to produce and survivethe breaks of continuity of the liquid in form of cavitation cavitiesunder such conditions. Known methods are not capable to providedecompression in liquid sufficient to boil it adiabatically. Theproposed device is capable to produce breaks of continuity of the liquiddue to high flowing speed and periodic full or partial interrupting ofthe flow. In this case the extremely powerful inertial forces inherentto the moving liquid can be realized and fluid flow continuity can beimplemented despite high hydrostatic pressure.

[0039] Break of a fluid flow continuity can be obtained also due tovarious hydraulic jars or other valve systems, but all of them requiretoo high hydraulic power, their designs are rather complicated (and notdurable) and high hydraulic shocks are generated in the pumped pipe.Also the repetition rate of such breaks is limited and it is notsufficient to maintain the continuous cavitation.

[0040] Technical Applicability

[0041] The proposed devices for hydrodynamic action on the wall of aborehole comprising the cavitating auto-oscillating devices are simpleby their design and providing minimum pressure drop (not more than 3 MPaat pumping rate of up to ˜30 liter/sec). In combination with interrupterof the discharge jet this device provides a pulsed regime of a circularaction on the wall of a well.

[0042] Field tests of said devices in deep wells showed that due todecolmatation of the productive rock one can increase the oil intakeflow by 2-3 times minimum and provide fast and effective cleaning of thelift and casing pipes from deposits and scale of different nature.

1. Device for hydrodynamic action on wall of a well comprising a casingjointed with the pipe conduit and inside of which casing the mechanismfor cavitating of flow of liquid, mechanism for directing and splittingof the flow and mechanism for interrupting of the discharge jets aresequentially placed in said order from the top of the device downwherein said mechanism for cavitating of flow of liquid is made in formof an auto-oscillating system.
 2. Device of claim 1, wherein said casingis jointed to the pipe conduit via a roller support.
 3. Device of claim1, wherein said mechanism for cavitating of flow of a liquid is made inform of a ball with its diameter ratio to inner diameter of the casingof 0.9-0.98 and comprises a limiter of axial motion of the ball. 4.Device of claim 1, wherein said mechanism for cavitating of flow of aliquid is made in form of a ball with its diameter ratio to innerdiameter of the casing less than 0.9 and comprises a limiter of axialmotion in form of a coil spring lower end of which is rigidly connectedto the casing and the upper end of which has a seat for the ball. 5.Device of claim 1, wherein said mechanism for cavitating of flow of aliquid is made in form of a cone the nose of which is directed counterflow, which cone is placed into a diffuser providing a clearance to letthe liquid flowing and a freedom for the cone to move axially.
 6. Deviceof claim 1, wherein said mechanism for cavitating of flow of a liquid ismade in form of a butterfly valve freely rotating around a transverselyshaft and the halves of which are oppositely convex in respect of therotation axis of said valve.
 7. Device of claim 1, wherein saidmechanism for interrupting of the discharge jets is made in form of thecylindrical roller bodies placed in the casing equidistantly ornon-equidistantly by a separator wheel and resting on a ball working asboth a roller support and a float valve. And the number of saidcylindrical bodies is either (n+1) or (n−1) where (n) is a number ofoutlet orifices.